One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,6)(7,8)(10,14)(11,17)(12,20)(15,21)(16,23)(18,22)(25,26,29,33)(27,30,34,37)(28,31,36,32)(35,38,40,39)(1,3,4,7)(2,5,6,8)(9,10,12,14,13,15,20,21)(11,18,19,23,17,16,24,22)(27,34)(30,37)(35,40)(38,39)(2,6)(5,8)(10,15)(14,21)(16,18)(22,23)(25,27,29,34)(26,30,33,37)(28,35,36,40)(31,38,32,39)(9,11,12,19,13,17,20,24)(10,16,14,22,15,18,21,23)(26,31)(28,36)(30,38)(32,33)(35,40)(37,39)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.